1. Field of the Invention
The present invention relates to an electronic apparatus and an auto wake-up circuit thereof, and more particularly, to an electronic apparatus of which auxiliary functions can still be maintained while it is in a sleep mode.
2. Description of the Related Art
With rapid popularity of hand-held devices in the modern life, people can enjoy the advantages of cellular phones, personal digital assistants (PDA) or portable multimedia players (PMP), etc. Also, more and more auxiliary modules are integrated into the hand-held devices involving technologies such as Global Positioning System (GPS), radio frequency identification (RFID), and other prospective applications. A sleep mode function is generally provided in the hand-held devices such that the hand-held devices can enter the sleep mode to reduce battery power consumption at some time after operations of certain functions have been stopped. However, the operations of other essential function modules such as RF chip modules, or auxiliary modules such as GPS, RFID modules, still need to be maintained during the sleep mode.
To reduce battery power consumption, these essential function modules or auxiliary modules need not perform full functions while the system is in the sleep mode. In the conventional approach, a base-band chip or an additional watch-dog chip in a hand-held device may generate a wake-up signal in order to control the operations of the auxiliary modules. Three conventional wake-up circuits are shown exemplarily as below.
1. The wake-up signals may be generated by hand-held devices. FIG. 1 is a schematic view of a system in which the wake-up signals are generated by a hand-held device. Wherein, an RF chip 6, coupled to a base-band chip 1, is for modulating and amplifying signals of the base-band chip 1 and for transmitting the same via an antenna. Alternatively, the signals received from the antenna are demodulated to base-band signals and are further processed by the base-band chip 1. Note that the base-band chip 1 is required to generate a plurality of specific programmable hardware signals for providing wake-up signals of different time points for RF chips and auxiliary modules respectively. However, during the sleep mode, to generate such specific hardware signals is bound to increase power consumption as well as circuit design complexity.
2. The wake-up signals of RF chips are shared. FIG. 2 is a schematic diagram illustrating the sharing of wake-up signals of RF chips. A similar function can be achieved by sharing the wake-up signals of the RF chip 6. However, certain complications may arise since a timing correcting circuit 2 is needed to correct timing of the wake-up signals due to possible differences in wake-up time between the RF chip 6 and an auxiliary module 7.
3. The wake-up signals are generated by watch-dog chips. FIG. 3 is a schematic diagram of a system in which wake-up signals are generated by a watch-dog chip; a watch-dog chip 3 is added to an auxiliary module 4 in order to generate the desired signals. By this approach, while the system enters or exits the sleep mode, the base-band chip 1 only needs to generate a signal rather than sharing the wake-up signals of the RF chip 6. Thus, the wake-up signal for the auxiliary module 4 is provided by the watch-dog chip 3. Nonetheless, although this is a simple approach, extra cost for the watch-dog chip 3 is incurred and the size of printed circuit board also increases meanwhile.
Accordingly, in view of the above drawbacks, it is an imperative of the present invention to provide an improved electronic apparatus and an auto wake-up circuit thereof, so as to maintain operations of auxiliary functions of the electronic apparatus during the sleep mode, and thus to lower manufacture costs as well as to reduce hardware volume.